1. Field of the Invention
The application relates to a method utilized in a wireless communication system and a communication device thereof, and more particularly, to a method of handling measurement in a wireless communication system and a related communication device.
2. Description of the Prior Art
A long-term evolution (LTE) system, initiated by the third generation partnership project (3GPP), is now being regarded as a new radio interface and radio network architecture that provides a high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNBs) and communicates with a plurality of mobile stations, also referred as user equipments (UEs).
In the LTE system, a user equipment (UE) may perform measurement to measure communication quality, such as quality of a frequency layer or strength of a radio signal, which is controlled by the E-UTRAN, due to mobility of the UE. Measurement can be divided into two types according to the current operating frequency of the UE, which are an intra-frequency measurement and an inter-frequency measurement. The intra-frequency measurement is predominantly performed for the mobility within the same frequency layer (i.e. between cells with the same carrier frequency), whereas the inter-frequency measurement is predominantly performed for the mobility between different frequency layers (i.e. between cells with different carrier frequencies). Moreover, the inter-frequency measurement is performed during uplink/downlink idle periods, such as a measurement gap configured by the network. During the measurement gap, both the uplink and downlink transmissions are prohibited, and thereby the inter-frequency measurement can be performed within the measurement gap.
Toward advanced high-speed wireless communication system, such as transmitting data in a higher peak data rate, LTE-Advanced system is standardized by the 3rd Generation Partnership Project (3GPP) as an enhancement of LTE system. LTE-Advanced system targets faster switching between power states, improves performance at the cell edge, and includes subjects, such as bandwidth extension, coordinated multipoint transmission/reception (COMP), uplink multiple input multiple output (MIMO), etc.
For bandwidth extension, carrier aggregation is introduced to the LTE-Advanced system for extension to wider bandwidth, where two or more component carriers are aggregated, for supporting wider transmission bandwidths (for example up to 100 MHz) and for spectrum aggregation. According to carrier aggregation capability, multiple component carriers are aggregated into overall wider bandwidth, where the UE can establish multiple links corresponding to the multiple component carriers for simultaneously receiving and/or transmitting.
In addition, COMP is considered for LTE-Advanced as a tool to improve coverage of high data rates, cell edge throughput, and system efficiency, which implies dynamic coordination among multiple geographical separated points. That is, when an UE is in a cell-edge region, the UE is able to receive signal from multiple cells, and the multiple cells can receive transmission of the UE.
In the LTE-Advanced system, a UE in a radio resource control (RRC) connected state is configured with multiple component carriers to receive data by the network (i.e. an eNB). In addition, the eNB can activate or deactivate any of the multiple component carriers by using a physical downlink control channel (PDCCH) order. Please note that, when one of the multiple component carriers is deactivated, the UE does not need to receive the corresponding PDCCH or physical downlink shared channel (PDSCH), nor require to perform channel quality indicator (CQI) measurement. Conversely, when one of the multiple component carriers is activated, the UE shall receive PDSCH and PDCCH, and is expected to be able to perform CQI measurement. However, the LTE-Advanced system does not clearly define whether the UE requires a measurement gap to measure an inter-frequency cell when one of the multiple component carriers is deactivated. In other words, the network does not know whether to configure the measurement gap to the UE or not. Improper configuration of the measurement gap may cause packet scheduling problems.
Furthermore, the abovementioned situation may occur in a universal mobile telecommunications system (UMTS). Dual cell operation is characterized as simultaneous reception of more than one high speed downlink shared channel (HS-DSCH) transport channel, and dual band operation is characterized as simultaneous reception of more than one HS-DSCH transport channel which are carried over more than one radio frequency band. Certain categories of UEs may be configured into dual cell operation/dual band operation in a CELL_DCH state, wherein dual cell operation/dual band operation may be activated and deactivated by high speed shared control channel (HS-SCCH) orders. Therefore, when the UE operated with the dual cell operation/dual band operation is configured with two carriers by a universal terrestrial radio access network (UTRAN), a serving node B of the UTRAN may deactivate one of the two carriers. However, the UMTS system does not clearly define whether the UE requires a measurement gap to measure an inter-frequency cell when one of the two carriers is deactivated.